Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer thinks the engine is using too much or too little fuel on one side of the engine. It's like if you were eating too much or too little at lunch.
The P0173 code indicates that the fuel mixture on bank 2 of the engine is not within the expected range. The engine control module (ECM) is unable to adjust the air-fuel mixture to the desired level.
P0173 is a diagnostic trouble code (DTC) for 'Fuel Trim Bank 2'. This code is triggered when the ECM detects that the fuel trim for bank 2 is out of the normal range. This can be due to a variety of issues such as a vacuum leak, faulty fuel injector, or a malfunctioning oxygen sensor.
• Check Engine Light is on
• Poor fuel economy
• Engine misfires
• Rough idling
• Reduced engine performance
• Vacuum leaks
• Faulty fuel injector
• Malfunctioning oxygen sensor
• Exhaust leak
• Faulty mass air flow sensor
Fuel Trim: Adjustments made by the engine control module to the air-fuel mixture.
Bank 2: The side of the engine opposite bank 1, usually the side without cylinder 1.
• Scan the vehicle with an OBD-II scanner to confirm the code.
• Inspect for vacuum leaks on bank 2.
• Check the oxygen sensor and mass air flow sensor for proper operation.
• Inspect fuel injectors for proper function.
• Repair any vacuum leaks found.
• Replace faulty oxygen sensor.
• Clean or replace the mass air flow sensor.
• Replace faulty fuel injectors.
• OBD-II scanner
• Vacuum gauge
• Multimeter
• Fuel pressure tester
$150 - $500
Moderate
• BMW 3 Series
• Mercedes-Benz C-Class
• Audi A4
• Regular maintenance and inspection of the fuel system.
• Ensure air filters are clean and replaced regularly.
• Use high-quality fuel to prevent injector clogging.
Engine Performance
• Do not ignore the check engine light; get it diagnosed as soon as possible.
• If experiencing poor fuel economy, have the vehicle inspected by a professional.
Repairs may be covered under the vehicle's emissions warranty. Check with your dealer.
P0173 has been a common code for vehicles with fuel system issues, particularly in European models.
Moderate – While the vehicle may still be drivable, it is important to address this issue to prevent further engine damage or reduced efficiency.
Driving with a check engine light on can lead to increased emissions and potential engine damage. It is advisable to have the vehicle inspected and repaired promptly.
• Engine at operating temperature
• Vehicle idling
Bank 2 refers to the side of the engine opposite bank 1, typically the side without cylinder 1.
Q: Can I drive my car with a P0173 code?
A: While the car may still be drivable, it's best to get it checked out to avoid potential damage.
Q: How do I fix a P0173 code?
A: Diagnosis is required to determine the exact cause. Common fixes include repairing vacuum leaks or replacing faulty sensors.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
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Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.